Patent application title: Trough heat collector element insulator

Abstract:

A concentrating solar collector heat collecting element insulating shield
has an elongated hemi-cylindrical body having an internal diameter
approximately equivalent to (able to physically engage to) the outer
diameter of the concentrating solar power (CSP) heat collecting element,
either the evacuated outer tube, the fluid-carrying inner tube, or both.
The device may have multiple layers of insulating/reflecting material,
sheet metal, polymer, composite, may have flanges, fingers or other
attachments to the CSP heat collecting element tube, or may be slightly
greater than 180 degrees in arc so as to grip the CSP heat collecting
element.

Claims:

1. A CSP heat collecting element insulating device for use on a CSP heat
collecting element having an outside diameter and length, the CSP heat
collecting element insulating device comprising:a body having a
semi-circular cross section and an elongated length, the semi-circular
cross section of the body having an inside diameter approximately equal
to that of such CSP heat collecting element outside diameter.

2. The CSP heat collecting element insulating device of claim 1, further
comprising:an arc of the semi-circular cross section, the arc being
greater than 180 degrees, whereby the device may maintain physical
engagement with such CSP heat collecting element.

3. The CSP heat collecting element insulating device of claim 1, further
comprising:an arc of the semi-circular cross section, the arc being less
than 180 degrees;at least one upper projection from the body and at least
one lower projection from the body, the upper and lower projections
cooperating to maintain physical engagement with such CSP heat collecting
element when the CSP heat collecting element device is placed on such CSP
heat collecting element.

11. The CSP heat collecting element insulating device of claim 1 used on a
CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter, further
comprising:a second body having a second semi-circular cross section and
a second elongated length, the semi-circular cross section of the body
having a diameter approximately equal to that of such CSP heat collecting
element;the first body semi-circular cross section inner diameter
approximately equal to such CSP heat collecting element outer evacuated
tube outer diameter; andthe second body semi-circular cross section inner
diameter approximately equal to such CSP heat collecting element inner
fluid-carrying tube outer diameter.

Description:

COPYRIGHT NOTICE

[0001]A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright owner
has no objection to the facsimile reproduction by anyone of the patent
document or the patent disclosure, as it appears in the Patent and
Trademark Office patent file or records, but otherwise reserves all
copyright rights whatsoever. 37 CFR 1.71(d).

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002]N/A

FIELD OF THE INVENTION

[0003]This invention relates generally to concentrating solar power
devices, and specifically to heat collector elements of concentrating
solar power devices.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH

[0004]This invention was not made under contract with an agency of the US
Government, nor by any agency of the US Government.

BACKGROUND OF THE INVENTION

[0005]Concentrating solar power (CSP) collectors consist of a long trough
of reflective material having a parabolic shape designed to focus the
sun's rays upon a long tubular heat collecting element (HCE) running the
length of the reflector. The HCE in turn consists of a metal tube through
which fluid is pumped. Usually, the HCE is a two tube design having an
inner (fluid carrying) tube and an outer tube as well. The outer tube is
normally glass with the interior cavity holding the inner tube and being
evacuated: the evacuated space between the two tubes serves to insulate
the hot inner tube from the ambient environment, at least in terms of
conductive heat transfer. When radiant sunlight hits the reflector, it is
reflected and concentrated on the HCE, resulting in the HCE becoming hot.
FIG. 1 is a PRIOR ART perspective front elevational view of a single
concentrating solar power collector with most ancillary equipment
removed. Concentrating solar power collector (CSP) 100 has reflector
trough 102 and heat collecting element (HCE) 104: sunlight falling on the
reflector 102 is concentrated on the HCE 104. Of particular note is that
the HCE becomes quite hot. Once hot, the HCE in turn becomes a source of
heat loss, that it is, it rejects heat into the environment around it.
This heat loss represents a loss of efficiency and energy from the solar
power system. Heat may be rejected by several means, principally via
radiation to the surroundings. (As noted previously, the evacuated outer
tube insulates against conductive heat loss. However, since the outer
tube must be transparent, it cannot stop all radiant heat loss.) Since
the most effective color for absorbing light is black, the inner HCE tube
may be a dark color. However, since the most effective color for
radiating heat is also black, the HCE fluid tube may be an effective
radiator, adding to the undesired heat loss. Additionally, the extent
that the outer glass tube gets hot (or in a hypothetical system lacking
an outer tube) convection of heat into air flowing around the HCE results
in heating of the air and loss of energy as well.

[0006]FIG. 2 is a PRIOR ART cross-sectional view of a heat collector
element designed to alleviate some of these problems. Concentrating solar
power heating element 200 shows a double tube system consisting of glass
outer tube 202 having within it evacuated chamber 204, meaning that
fluid-carrying metallic inner tube 206 having therein fluid conduit 208
suffers a much reduced loss from convection of air past the HCE. However,
inner tube 206 may still radiate heat outward to or through outer tube
202. Since the outer surface of glass tube 202 also gets very hot,
convective heat loss from that surface also occurs.

[0007]Consideration of the structure of the device shows that sunlight
concentrated by the reflector falls primarily on one face of the device.
Unconcentrated sunlight directly from the sun is much weaker and is the a
negligible source of energy input on the back side of the device.

[0008]It would be preferable to take advantage of this asymmetrical energy
flux to provide for more effective insulation of the HCE.

SUMMARY OF THE INVENTION

[0009]General Summary

[0010]A CSP heat collecting element insulating shield has an elongated
hemi-cylindrical body having an internal diameter very slightly greater
than (or approximately equivalent to, meaning able to physically engage
to) the outer diameter of the CSP heat collecting element, either the
evacuated outer tube, the fluid-carrying inner tube, or both. The device
may have multiple layers of insulating/reflecting material, sheet metal,
polymer, may have flanges, fingers or other attachments to the CSP heat
collecting element tube, or may be slightly greater than 180 degrees in
arc so as to grip the CSP heat collecting element. In diverse
embodiments, a positive standoff (for example, 1/32 inch) between the
interior diameter of the device and the outer diameter of the HCE tube it
is affixed to can be assured by geometry of the fingers or other
attachments, or by use of dimples, shims, ridges or other suitable means.

[0011]Summary in Reference to Claims

[0012]It is therefore a first aspect, advantage, objective and embodiment
of the invention, in addition to those discussed previously, to provide a
concentrating solar power (CSP) heat collecting element device for use on
a CSP heat collecting element having an outside diameter and length, the
CSP heat collecting element insulating device comprising: [0013]a body
having a semi-circular cross section and an elongated length, the
semi-circular cross section of the body having an inside diameter
approximately equal to that of such CSP heat collecting element outside
diameter.

[0014]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device further
comprising: [0015]an arc of the semi-circular cross section, the arc
being greater than 180 degrees, whereby the device may maintain physical
engagement with such CSP heat collecting element.

[0016]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device further
comprising: [0017]an arc of the semi-circular cross section, the arc
being less than 180 degrees; [0018]at least one upper projection
("finger") from the body and at least one lower projection ("finger")
from the body, the upper and lower projections ("fingers") cooperating to
maintain physical engagement with such CSP heat collecting element by
clipping or gripping when the CSP heat collecting element device is
placed on such CSP heat collecting element.

[0019]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device further
comprising: [0020]an attachment to such CSP heat collecting element.

[0021]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device wherein
the attachment further comprises one member selected from the group
consisting of: a braze weld, a weld, solder, adhesive, bolts, tabs,
detents, hooks, studs, rivets and combinations thereof.

[0022]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device wherein
the elongated length is approximately the same as such CSP heat
collecting element length.

[0023]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device wherein
the body is sheet metal.

[0024]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device wherein
the body is high temperature polymer or composite.

[0025]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device used on
a CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter, wherein:
[0026]the semi-circular cross section inner diameter is approximately
equal to the inner fluid-carrying tube outer diameter.

[0027]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device used on
a CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter, wherein:
[0028]the semi-circular cross section inner diameter is approximately
equal to the outer evacuated tube diameter.

[0029]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device used on
a CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter, further
comprising: [0030]a second body having a second semi-circular cross
section and a second elongated length, the semi-circular cross section of
the body having a diameter approximately equal to that of such CSP heat
collecting element; [0031]the first body semi-circular cross section
inner diameter approximately equal to such CSP heat collecting element
outer evacuated tube outer diameter; and [0032]the second body
semi-circular cross section inner diameter approximately equal to such
CSP heat collecting element inner fluid-carrying tube outer diameter.

[0033]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device used on
a CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter, further
comprising: [0034]at least one standoff device dimensioned and
configured to maintain a standoff between the body inside diameter and
the CSP heat collecting element outside diameter.

[0035]It is therefore another aspect, advantage, objective and embodiment
of the invention to provide a CSP heat collecting element device used on
a CSP heat collecting element having an inner fluid-carrying tube and an
outer evacuated tube, respectively having an inner fluid-carrying tube
outer diameter and an outer evacuated tube outer diameter; wherein the
standoff device further comprises: [0036]at least one dimple.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a PRIOR ART perspective front elevational view of a single
concentrating solar power collector with most ancillary equipment
removed.

[0038]FIG. 2 is a PRIOR ART cross-sectional view of a heat collector
element.

[0039]FIG. 3 is a cross-sectional view of a first embodiment of the
invention on the evacuated outer tube.

[0040]FIG. 4 is a cross-sectional view of a second embodiment of the
invention on the fluid-carrying inner tube.

[0041]FIG. 5 is a cross-sectional view of a third embodiment of the
invention on the fluid-carrying inner tube, showing attachment of the
device to the tube.

[0042]FIG. 6 is a perspective frontal view of a fourth embodiment of the
invention.

[0043]FIG. 7 is a perspective frontal view of a fifth embodiment of the
invention.

[0044]FIG. 8 is a cross-sectional view of a sixth embodiment of the
invention.

[0045]FIG. 9 is a cross-sectional view of a seventh embodiment of the
invention on the evacuated outer tube.

[0071]For purposes of the present application, "approximately equal" or
"slightly greater than" means a diameter or length able to make physical
engagement with another diameter or length by means of being the same
within a close tolerance, usually meaning a diameter at least one or two
mils greater than the diameter of the HCE tube to be gripped or a length
at least one or two mils less than the length of the HCE tube to be
gripped. However, if the materials are flexible, even one or two mils
difference may not be necessary, while if the material is not flexible or
the configuration is not conducive to a tight grip, a diameter more than
one or two mils greater may fit the applicant's chosen definition. This
is important as the retrofit embodiments of the invention allows easy
installation to the installed base of CSP systems, while the original
equipment embodiments of the invention may be more easily manufactured.
In addition, the slight gap shown in the diagrams in between the inner
surface of the insulating shield and the outer surface of the HCE tube to
which it is attached assures the insulating ability of the device. In
diverse embodiments, a positive standoff (for example, 1/32 inch) between
the interior diameter of the device and the outer diameter of the HCE
tube it is affixed to can be assured by geometry of the fingers or other
attachments, or by use of dimples, shims, ridges or other suitable means.

[0072]FIG. 3 is a cross-sectional view of a first embodiment of the
invention on the evacuated outer tube. Evacuated outer tube 302 may be
seen to have shield device body 310. While the shield device may be
original equipment, it may also be a retrofit which simply slips onto the
HCE. It will be appreciated from FIG. 3 and FIG. 1 that the HCE has a
length and an outer diameter, and that the device may be made with a
length and diameter which match the HCE, so as to allow easy
installation. In alternative embodiments, the device may be made in a
standardized length shorter than the HCE length, then short lengths may
be installed as desired or practical onto the HCE.

[0073]In use, the shield will act to insulate the side of the HCE which is
facing away from the reflector trough, reducing heat losses by radiation,
convection and/or conduction.

[0074]FIG. 4 is a cross-sectional view of a second embodiment of the
invention on the fluid-carrying inner tube. Fluid-carrying inner tube 406
rather than the outer tube is the carrier for the shield device 410. In
this case, the length and diameter of the HCE which are important are the
length and diameter of the interior tube.

[0075]Note that in CSP systems which may have only a single tube, this
configuration is the default configuration, though such CSP systems are
at best rare, due to the fact that the evacuation is usually necessary
for economical operation.

[0076]In general these configurations are held onto the tube simply be a
physical engagement thereto, which may be clamping or clasping, for
example. In a simple preferred embodiment, the device is held on by
virtual of having an arc of a circle measuring slightly more than 180
degrees. The degree of arc in excess of 180 will depend on the ductility
and nature of the materials used in the device and HCE, for example, with
sheet metal or softer polymers an arc of 190 or 210 degrees is perfectly
possible, as the material will allow itself to pass over the HCE easily.
With harder polymers, metals or the like, this can be reduced, as the
material will have less give and will thus hold itself on with a smaller
angle, and will require a smaller angle in order to fit on. Angles of
approximately 181 degrees can be envisioned.

[0077]FIG. 5 is a cross-sectional view of a third embodiment of the
invention on the fluid-carrying inner tube, showing attachment of the
device to the tube. Assuming material thermal compatibility, shield
device 510 may have attachment 512 used to secure it to the tube. The
attachment 512 may be a braze weld, a weld, solder, adhesive, bolts,
tabs, detents, hooks, studs, rivets, combinations thereof and so on.

[0078]FIG. 6 is a perspective frontal view of a fourth embodiment of the
invention. Shield device body 610 is shown in perspective, without the
HCE, for clarity. This embodiment may correspond to any of the first
three embodiments.

[0079]FIG. 7, however, is a perspective frontal view of a fifth embodiment
of the invention, showing for example purposes two different types of
projections or fingers. Shield device body 710 has fingers or projections
which allow the device body to subtend an arc of less than 180 degrees
yet still have simple physical engagement. First type of finger 714 and
second type of finger 716 are exemplary only, any shape of finger may be
used. Note that having two or more different types/shapes of fingers or
attachments on a single device is perfectly acceptable, however in
practice having only a single type of attachment is a bit more likely.

[0080]Such embodiments may be used in "deep trough" designs in which the
CSP reflector trough is deeper and radiates to a wider arc of the HCE. On
the other hand "shallow trough" designs, in which the reflector trough is
less than 180 degrees, would likely be more acceptable for use with the
embodiments having a greater than 180 degree arc.

[0081]FIG. 8 is a cross-sectional view of a sixth embodiment of the
invention. Shield device body 800 may be composed of more than a single
layer. For example, it might have a first layer 820, a second layer 822
and a third layer 824. These layers might be a combination of reflective
and refractory materials such as a first layer of foil or reflective
coating, a second layer of insulating material, and a third layer of
structural material or the like. One, two, three or more layers may be
used in any embodiment.

[0082]FIG. 9 is a cross-sectional view of a seventh embodiment of the
invention on the evacuated outer tube. In embodiments, a positive
standoff may be desirable or necessary. The standoff may be 1/32 inch but
it may be larger or smaller as necessary for installation, thermodynamic
efficiency and other considerations. The standoff between the interior
diameter of the device 910 and the outer diameter of the HCE tube 902 it
is affixed to can be assured by geometry of the fingers or other
attachments, or by use standoff devices 990, such as dimples, shims,
ridges or other suitable means.

[0083]In the presently preferred embodiment and best mode presently
contemplated for carrying out the invention, the device may be
standardized to standard HCE sizes and provided in lengths shorter than
the HCE, with multiple devices used to cover the length of the HCE.

[0084]The disclosure is provided to render practicable the invention by
those skilled in the art without undue experimentation, including the
best mode presently contemplated and the presently preferred embodiment.
Nothing in this disclosure is to be taken to limit the scope of the
invention, which is susceptible to numerous alterations, equivalents and
substitutions without departing from the scope and spirit of the
invention. The scope of the invention is to be understood from the
appended claims.